Project Background

Naturally occurring radioactive elements have been present in rocks and soils since the formation of the earth. Exposure from natural radionuclides in the ground varies with location and is mainly due to differences in the geology and soil type. The main sources of exposure from natural radioactivity in the ground is as a result of gamma radiation from Potassium-40 (K-40), Uranium-238 (U-238) and Thorium-232 (Th-232).  There is an additional contribution from artificial radioactivity present in Irish soils as a result of fallout from nuclear weapons testing in the past, nuclear accidents (for example, the Chernobyl accident), and authorized releases from nuclear facilities abroad. 

Several studies of gamma dose rates from natural and artificial radionuclides in Ireland were conducted in the 1980s and 1990s, and these have formed the basis for the estimation of terrestrial gamma radiation doses in the periodic assessments which are carried out by the EPA on the average annual radiation doses received by the Irish population from all sources of ionising radiation. The GRaDE project aims to develop a better understanding of the geographical distribution of natural and artificial gamma-emitting radionuclide concentrations in the Irish terrestrial environment with a view to providing a more accurate, up to date estimate of the average annual effective dose that a member of the Irish public receives as a result of exposure from terrestrial gamma radiation. By making use of a combination of high-resolution gamma spectrometry measurements, direct gamma dose rates gathered in the field using calibrated field monitors, and the gamma dose rates inferred from available aerial radiometric data on uranium, thorium and potassium concentrations, and Caesium (Cs-137) deposition from the Tellus programme, a set of new, high-resolution maps on radionuclide concentrations and gamma ray dose rates throughout Ireland will be generated using appropriate Geographical Information Systems (GIS) tools. These maps, together with information on population density, will be used to generate a map of outdoor gamma ray doses in Ireland and to investigate the range and average annual doses to a member of the Irish public arising from terrestrial gamma radiation.